INFLUENCE OF THE DEMAND FOR FOOD. 57 



nearly constant supply, and have no receptacle for collecting 

 it at its immediate entry; the sap, as we have seen, passing 

 at once into the cellular tissue of the plant, where the pro- 

 cess of its gradual elaboration is commenced. Animals, on 

 the other hand, are capable of receiving at once large sup- 

 plies of food, in consequence of having an internal cavity, 

 adapted for the immediate reception of a considerable quan- 

 tity. A vegetable may be said to belong to the spot from, 

 which it imbibes its nourishment, and the surrounding soil, 

 into which its absorbing roots are spread on every side, 

 may almost be considered as a part of its system. But an 

 animal has all its organs of assimilation within itself, and 

 having receptacles in which it can lay in a store of provi- 

 sions, it may be said to be nourished from within; for it is 

 from these interior receptacles that the lacteals, or absorb- 

 ing vessels corresponding in their office to the roots of ve- 

 getables, imbibe nourishment. Important consequences 

 flow from this plan of structure; for since animals are thus 

 enabled to subsist for a certain interval without needing any 

 fresh supply, they are independent of local situation, and 

 may enjoy the privilege of moving from place to place. 

 Such a power of locomotion was, indeed, absolutely neces- 

 sary to beings which have their subsistence to seek. It is 

 this necessity, again, which calls for the continued exercise 

 of their senses, intelligence, and more active energies; and 

 that lead, in a word, to the possession of all those higher 

 powers which raise them so far above the level of the ve- 

 getable creation. 



VOL. II. 



